Quaternary ammonium salts have the general formula of: EQU [(CH.sub.3).sub.4 N].sup.+ X.sup.- (1)
where X is a halogen such as iodine, chlorine or bromine. A variety of quaternary ammonium compounds are available and widely used as disinfectants and biocides and to treat items that may undesirably support microbial growth. For example, quaternary ammonium salts are used to treat carpeting, walls, various commercial products such as sponges and fabrics, and even water. They are also used to rehabilitate "sick buildings," particularly after floods and water leaks, and reduce odors caused by mildew, fungus and bacterial growth in damp basement areas.
Most quaternary ammonium salts commercially available are generally pre-packaged in water or alcohol solutions of approximately 2-3% or less quaternary salt concentration. They are applied to substrates such as carpets, walls, floors, to kill the bacteria. The method of application often relies on delivering the quaternary ammonium salt in a fine spray. When treating fabrics, sponges, bedding, and similar products, the concentration of the quaternary ammonium salts generally can be much lower, e.g., less than 1%.
Despite knowledge of the common usage of quaternary ammonium salts for imparting antimicrobial properties, a method was not known for treating medical devices and supplies and other consumer products that was biocompatible.
Applicants' method uses quaternary ammonium salts of the general formula of: ##STR1## wherein R.sub.1 and R.sub.2 are methyl (--CH.sub.3) groups; R.sub.3 is octadecyl (CH.sub.3 (CH.sub.2).sub.17 --); and R.sub.4, R.sub.5 and R.sub.6 are methoxy (--OCH.sub.3) groups. Applicants' method can be used to treat, either during or after manufacture, textile materials, particularly medical devices and supplies, such that such devices and supplies have long-lasting, non-leaching, biocidal properties on the surface and are not toxic to the host organism. The treatment involves converting the methoxy groups to OH groups through hydrolysis and then polymerizing through condensation of the OH groups to form siloxane bonds and water.
More specifically, because catheter infections are the leading cause of hospital or long-term care infections, numerous attempts have been made to create a catheter that is antimicrobial. Most antimicrobial catheters rely on the impregnation of antibiotics to achieve a catheter that is resistant to bacterial infection. Unfortunately, this use of antibiotics results in increased resistance to antibiotics, a significant problem for immuno-compromised patients. It also leads to the subsequent long-term inefficacy of such catheters.
Further, some antimicrobial catheters use a coating treatment to provide a vehicle for entrapping drugs onto the catheter surface but permit subsequent diffusion into the biological environment. Many such treatments rely upon a polyurethane in a solvent to entrap antibiotic pharmaceutical agents.
Thus, despite numerous and concerted efforts, a cost-efficient method has not been devised to impart non-leaching, biocompatible, antimicrobial properties to surfaces. In particular, despite the long felt need for such method or device in the catheter industry, until Applicants' invention, no such method or device existed.
Interpenetrating polymer networks (IPNs) are well known in the art. They are prepared in a variety of ways and the technical literature is replete with the technology for the manufacture of such IPNs. The most common ways to create IPNs are (1) by blending two or more polymers in an internal mixer using temperature, mixing time and torque to obtain a blended or grafted IPN, and (2) by "swelling," i.e., expanding, a higher polymer with a monomer or a solution of a monomer and polymerizing the monomer to a polymer in situ.
In this latter case, when monomer (A) is polymerized to form a polymer (A) in a host or substrate polymer (B), such as silicone or polyurethane elastomer, a high degree of permanence can be established for polymer A. That is, polymer A can only be removed to a limited degree when the IPN is extracted by an organic solvent or water. Therefore, such an IPN has long term stability.
However, until now, IPNs of polymerized quaternary ammonium salt monomers have not been used to impregnate the surfaces of medical devices and supplies to impart antimicrobial properties to such devices and supplies. Applicants' technique accomplishes this in such a manner that does not compromise their biocompatibility.
It is an object of this invention to provide a method for creating an interpenetrating network on the surface of devices and supplies that is biocompatible and antimicrobial.
It is a further object of the invention to provide a method for creating a biocompatible and antimicrobial surface for consumer products.
It is an object of the invention to incorporate antimicrobial activity into devices that may be implanted in or used on living organisms.
It is a further object of the invention to provide an antimicrobial catheter that is not dependant on antibiotic drugs for antimicrobial activity.
It is an object of this invention to provide a process for creating a polymeric coating having antimicrobial properties that can be applied to various medical device and supply surfaces.
Other objects of the invention will be obvious upon reading the following specification and claims.